1. Field of the Invention
This invention relates to apparatus for supporting and guiding a sub-lance which carries out measurements and/or taking of samples in a steel furnace.
2. Description of the Prior Art
In the preparation of steel in a steel furnace, use is often made of a sub-lance in order to take temperature and/or oxygen measurements during the refining process, and also to take samples on the basis of which the further progress of the process is controlled. For this purpose a water-cooled sub-lance is briefly put into the furnance so that a measurement or sampling probe reaches into the melt. The sub-lance is then removed.
An apparatus for supporting the sub-lance and guiding its movement is disclosed in Japanese laid-open patent application no. 90506/75 (application no. 138129/73 dated Dec. 13, 1973) and comprises a vertical guide track, a sub-lance carriage which moves along this guide track and in which the sub-lance is suspended, and a sub-lance guide which moves along the same guide track below the sub-lance carriage. Connecting means including a supporting cable cause the sub-lance guide to be located in dependence on the position of the sub-lance carriage.
Because of the great length of the sub-lance and the conditions in which it is used, accurate guidance with the aid of a sub-lance guide as described above is important. During the time when the sub-lance is lowered into the furnace, the sub-lance guide should be located as close as possible to the entry point of the sub-lance into the furnace in order to maintain the guidance of the sub-lance. The guide must be raised when the sub-lance is at its highest position, in order to maintain contact with the sub-lance, because when the sub-lance is removed from the furnace, there must be enough room to change the measuring probe, which means that the lance must be removed some distance above the furnace. There is thus the requirement that not only the sub-lance carriage in which the sub-lance is suspended must be movable along the guide track, but the sub-lance guide also must be movable even if over a shorter distance only.
In the Japanese patent publication mentioned above, the sub-lance guide is suspended on a cable and balanced by a counter-weight via a pulley. Special apparatus must be provided in order to ensure that the sub-lance guide and the cable is moved suitably in dependence on the position of the sub-lance or the sub-lance carriage.